1. Field of the Invention
This invention relates to an apparatus for selectively forming different flute types of single-faced corrugated board sheets in one single facet.
2. Description of the Related Art
There has been known a single facer which forms a single-faced corrugated board sheets by allowing a corrugating medium to have a corrugation with a predetermined pitch size, and pasting the medium with a liner at the crests of corrugation using a glue. The single facer comprises an upper fluted roll and a lower fluted roll both having a wavy flutes on the circumference, which are rotatably supported on a frame in such a way that their fluted circumferences may be engaged in a vertical relationship, and a press roll which is designed to be brought into press contact with the lower fluted roll through the corrugating medium and liner. The corrugating medium is allowed to have a predetermined corrugation or flutes as it is fed between the upper fluted roll and the lower fluted roll under engagement of their fluted circumferences, and also a glue is applied to the crests of corrugation by a gluing roll provided in a gluing mechanism. The liner being fed from the opposite side of the corrugating medium through the press roll is bonded to the crests of the corrugating medium as nipped between the press roll and the lower fluted roll so as to form a single-faced corrugated board.
Single-faced corrugated boards are generally classified into Flute A, Flute B, Flute C, Flute D, Flute E, Flute No. 4, Flute No. 5, etc. depending on the depth of the flutes to be formed on the corrugating medium and the standard number of crests per 30 cm. The flute type can be selected depending on the flute profile of the upper and lower fluted rolls to be disposed in the single facer.
As described above, there are many flute types in the single-faced corrugated boards and the flute type is dependent upon the flute profiles of the upper and lower fluted rolls incorporated in the single facer. Accordingly, in order to form different types of single-faced corrugated boards in one single facet, there has been employed a constitution, in which a plurality of single facers are arranged in the corrugator line to make selective operation of the desired single facer.
In such system, however, the installation cost is of course doubled because of the plurality of single facers disposed, and besides there are many other problems involved with respect to the installation area, operability, incidental equipment, etc. for the system to be put into practical uses. Moreover, the combination of different flute types of single-faced corrugated boards to be formed selectively cannot be selected at random, but restricted to predetermined combinations, for example, flute A and flute E, flute B and flute E, and flute C and flute E. Under such circumstances, there are proposed various types of single facers, in which two sets of fluting units having different types of flute profiles are disposed in one single facer, whereby to form different flute types of single-faced corrugated boards by selectively using these fluting units.
For example, there is "A single facer" disclosed in Japanese Unexamined Patent Publication (Kokai) No. Sho 61-58881 which was previously filed by the present applicant. In the single facer according to the previous invention, as shown in the drawings attached to the Publication thereof, a first fluting unit consisting of a pair of fluted rolls and a second fluting unit also consisting of a pair of fluted rolls are disposed, respectively, diagonally above and diagonally below a press roll which can selectively be combined with these two units, and thus different types of single-faced corrugated boards can be formed by selecting the first fluting unit or the second fluting unit to be combined with the press roll.
In the single facer described above, different types of single-faced corrugated boards can be formed merely by shifting the press roll, and this system can adequately be evaluated highly. However, since the press roll itself is very heavy, a large-scaled supporting mechanism and a large-scaled adjusting mechanism are required so as to achieve shifting of the press roll and adjustment thereof with high positioning accuracy when it is stopped. Further, since the press roll is designed to be rotationally driven in synchronization with the running speed of the corrugating medium and liner, a complicated constitution of mechanism for connecting the press roll with a drive source, which permits shifting of the position of the press roll under the adjustment, becomes necessary, leading to cost elevation.
The press roll is of a large-diameter metallic roll which is normally urged toward the lower fluted roll of the first or second fluting unit so as to apply a predetermined nip pressure to the corrugating medium and the liner passing between these two rolls. Since flutes consisting of continuous alternative repetition of crests and troughs are formed at a predetermined pitch on the circumference of the lower fluted roll, the rotation center of the lower fluted roll and that of the press roll shift slightly as the point of press contact therebetween shifts from the trough to the crest or vice versa. Thus, as the result that the rotation centers of these rolls make cyclic reciprocating motions to be closer to or farther from each other as they rotate, great vibration and big noise are generated during formation of the single-faced corrugated board, causing the working environment in the plant to be worsened considerably. Besides, since both the press roll and the lower fluted roll are made of rigid metallic materials, an impact is periodically applied to the press roll (so-called the hammer phenomenon) every time the crests of the lower fluted roll are abutted against the press roll. Accordingly, linear press marks corresponding to the pitch of the crests of the lower fluted roll are formed horizontally on the surface of the liner in the thus formed single-faced corrugated board, disadvantageously.
In the single facer where a press roll and a lower fluted roll are employed as described above, these two rolls are brought into linear contact with each other via the corrugating medium and liner, so that the corrugating medium and the liner are nipped therebetween merely over a very narrow zone. Accordingly, if the speed of forming a single-faced corrugated board is set at a high level to shorten the time that the corrugating medium and liner pass between these two rolls, it is liable that the corrugating medium fails to be securely pasted with the liner. Thus, high-speed running of the single facer has been difficult. In addition, due to the same reason, pasting of a thick corrugating medium with a thick liner cannot successfully be achieved, disadvantageously.
This invention has been proposed in view of the disadvantages inherent in the prior art single facers provided with a plurality of fluting units which can form single-faced corrugated boards of different flute types and in order to overcome them in a successful manner, and is directed to provide an inexpensive single facer having a simple structure, which can cope with high-speed formation of single-faced corrugated boards and also can minimize vibration or noise during the operation.